The invention relates to extracting solid samples of marrow from a bone marrow cavity and the aspiration of fluid marrow without removing the device from the incision.
In the prior art, biopsy needles have had the disadvantages of collecting skin tissue and blood mixed with marrow specimens so as to prevent the obtaining of good samples. With these needles it is difficult, even with repeated attempts, to obtain adequate specimens, particularly from patients with myelofibrosis and depleted, fatty bone marrows.
Aspirated bone marrow taken with the prior art needles is typically not truly representative of the marrow as it tends to be composed of a mixture of particles of the marrow and peripheral blood. In these situations the gross appearance and the total nucleated cell count of the aspirated fluid do not furnish reliable estimates of the cellularity. It has been found that these types of samples from the same marrow source have wide variations in the total counts of nucleated cells. This has resulted in conflicting descriptions of normal and abnormal marrows. To overcome these problems in the prior art, the additional steps of mixing the aspirate with an anticoagulant and centrifuging the mixture, and examining the sediment have been used. Another method is to make smears and imprints of particles of solid marrow selected from the aspirate.
The failure to obtain good samples has required performance of multiple aspirations and in some cases surgical trephine for biopsy has had to be undertaken where repeated aspirators have failed to yield marrow cells or particles of diagnostic value.